The present invention relates to a system for selectively supplying a diesel engine with diesel fuel only or with a combination of diesel fuel and a gas fuel such as natural gas or propane, and for controlling operation of the engine in both fuel supply situations.
Dual fueled engines, using natural gas in the intake system and diesel pilot fuel to ignite the mixture, offer economic benefits with regard to lowering fuel costs. A stationary engine, used for irrigation or generator applications, offers high natural gas utilization due to its high load factor.
Currently available natural gas engine fumigation systems use mechanical means to meter the natural gas, such as either venturi valves in combination with pressure regulators or mechanically controlled throttle valves. These systems do not allow for precise metering over the engine operating range. In fact, such systems typically included mechanical governing or no governing at all, except venturi type mixers in the intake system. Such systems are not very accurate. As a result, the engine may be over-fueled and harmed or destroyed, or it may operate in an unsatisfactory manner. Additionally, such systems do not adjust diesel engine operation to optimize the use of natural gas. Furthermore, the user of such a system must decide if the engine should be run on dual fuel or on diesel. Also, such systems do not provide for safety shutdowns when using natural gas fuel.